This invention relates to a process for producing insoluble collagen products, collagen-based protein ingredients, water-dispersible collagen-based protein ingredients, and reduced-fat collagen-rich protein ingredients from animal skins tissues, particularly, poultry skin tissues. The ideas of converting pig skin, cowhide, and animal bones to commercial products, leather, collagen, and gelatin are well-established art. Information relevant to attempts to address these problems can be found in U.S. Pat. Nos. 2,979,438; 4,176,199; 3,398,677; 4,295,894; and Ockerman, H. W. and Hansen, C. L., Animal By-Product Processing and Utilization (2000). In the embodiments of the present invention, an unconventional technique was used in a new application, that is, poultry skins. In the production of skinless turkey and chicken products, skins and skins containing adhering muscle flesh are by-products. The use of these by-products are very limited. In recent years, there has been a need to add value to million of tons of poultry skins produced annually, a valuable source of potential revenue for both the poultry meat producer and the ingredient manufacturer. With U.S. broiler meat and turkey meat production reaching billions of pounds, the tremendous tonnage of poultry skins as by-products that would otherwise be disposed of or under-valued as inedible rendered fractions, renders a need to convert such by-products to value-added collagen-based protein ingredients.
Collagen is the most abundant protein in mammals (See U.S. Pat. No. 5,043,426 to Goldstein). Chemically, collagen is the fibrous protein that contributes to the unique physiological functions of connected tissues in the skin, tendon, bones, and cartilage. The structural unit is tropocollagen composed of 3-polypeptide chains, designated α1, α2, and α3, that form a triple helical structure stabilized by hydrogen bonds. This structure accounts for its rod-like form and rigid properties. The amino acid sequence of collagen is remarkably regular; nearly every third residue is glycine (gly-x-y triplet) in a region spanning more than 1,000 residues. Collagen molecules contain approximately 33% glycine, 22% proline, 11% hydroxyproline, and 0.7% hydroxylysine. From a nutritional standpoint, collagen is devoid of tryptophan, low in methionine, cysteine and tyrosine. Collagen contains two uncommon amino acids, 4-hydroxyproline and 5-hydroxylysine. Additionally, collagen Type I, is the most abundant form of collagen, with widespread distribution within the body. While the skin is composed mostly of Type I collagen, it is not unlikely to find Types II and III.
Collagen denatures at temperatures above 4° Celsius to a mixture of random coils comprising single, double, and triple strands. Upon controlled cooling below the melting temperature, Tm, reformation of the helical forms occurs, a phenomenon that accounts for its ability to form cold-set thermal reversible gels. Also, collagen swells out, but does not solubilize in water per se. Rather, acid, base, heat, and certain protease enzymes are used to facilitate solubility. Common sources of collagen are animal hides, skins, and bones. These sources represent commercial raw materials for leather or gelatin production. The unique physiochemical characteristics of collagen enable their use in a variety of food and pharmaceutical products.
Each year, over 200,000 metric tons of animal-derived collagen and gelatin are used in foods, pharmaceuticals, and cosmetic products. Most of the collagen and gelatin are derived from cow (bovine) and pig (porcine) skins. Most manufacturers use collagen and gelatin produced primarily from bovine by-products. Recently, there have been concerns among consumers and regulatory bodies regarding bovine-derived products emanating from reported incidents of bovine spongiform encephalopathy (BSE). BSE (also known as Mad Cow Disease) is a chronic, degenerative neurological disorder of cattle that belongs to a family of diseases known as transmissible spongiform encephalopathies (See Mermelstein, N. H., Comprehensive BSE Risk Study Released, Food Technology, January 2002, 56 (1), 75–76, incorporated herein by reference). BSE, which is known in the art to have “specified risk materials”, are transmitted from bovine tissues to humans. (See Calza L., Manfred, R., Chiodo F., Epidemics of bovine spongiform encephalopathy and new variant of Creutzfeldt-Jakob disease in humans. Most recent findings on prion disease, Recenti Prog Med. 2001 February.; 92(2): 140–9, herein incorporated by reference). Also included in that family of illnesses is vCJD, which is believed to be caused by eating neural tissue, such as brain and spinal cord from BSE-affected cattle (See Mermelstein, N. H., supra).
The public's concern and fear, especially in the European Union, about BSE is in part providing market incentives to seek alternative sources of collagen. The absence of BSE-related issues in poultry products plus the tremendous tonnage of available poultry skins make poultry skins a very desirable raw material source of collagen and gelatin.
In an embodiment of the present invention, the behavior of collagen during heating, shearing, and cooling was exploited to produce the products described herein without the use of acids and/or protease enzymes. By varying process parameters, embodiments of the present invention enables considerable flexibility in processing manipulation that can lead to the production of products of a wide range of physicochemical properties. The derived protein ingredients are highly functional providing gelling, emulsifying, firming, water-binding, and flavor-enhancing properties. There is therefore a need in the art for a process that provides an economical viable option to convert poultry skins to collagen-based functional protein ingredients of high value.
Accordingly, it is an object of the present invention to provide a process to simultaneous extract and fractionate collagen-rich proteinaceous materials and fractions thereof from poultry skins.
A further object of the invention is to provide the proteinaceous extracts as value-added protein ingredients.
A further object of the invention is to provide insoluble and soluble collagen products, collagen-based protein ingredients, water-dispersible collagen-based protein ingredients, and reduced-fat collagen-rich protein ingredients from poultry skin tissues.
Still a further object of the invention is to extract and fractionate collagen-rich proteinaceous materials and derivatives thereof from poultry skins and the development of the proteinaceous materials to collagen-based ingredients.
It is still a further object of the invention to develop the proteinaceous material to collagen-based protein ingredients that function as meat replacer, texturizer, binder/filler, stabilizer, or protective colloids in processed meat products.
It is still a further object of the invention, to produce soluble collagen (which is synonymous with commercial gelatin) by an unconventional, non-chemical technique, of recovering the liquid phase and separating it into fat and soluble collagen-rich fractions. The soluble collagen has potential utility in food (e.g., ice cream, mayonnaise dressing) and non-food applications, such as pharmaceuticals (e.g., capsules and coating for pills) and cosmetics.
Still further objects of the invention will become apparent in the following disclosure.